1. Field of the Invention
The present invention relates to a tube joint. Specifically, the present invention relates to a tube joint functioning as protecting a joining portion of the tube joint from an external force.
2. Description of the Related Art
As shown in FIG. 6, a conventional tube joint generally comprises a tubular first tube joint member 300, a tubular second tube joint member 302 which is joined to the first tube joint member 300, a sleeve 304 which is attached to a joining portion of the first and second tube joint members 300, 302 and which functions to join and release the first and second tube joint members 300, 302, a compressive coil spring 306 which urges the sleeve 304 in the direction to join the first and second tube joint members 300, 302 to one another, and a plurality of ball members 308 which function to engage the first and second tube joint members 300, 302 with each other.
The first tube joint member 300 comprises a cylindrical member 312 which has its front to be inserted into the sleeve 304 and its rear formed with a female thread 310, and a cylindrical joining member 314 to be screwed into the female thread 310 of the cylindrical member 312. An accommodating space 318 for accommodating a valve plug 316 is formed at a front of the joining member 314. A closing plate 324 having a slit 322 for inserting a part of the valve plug 316 therethrough is installed between the cylindrical member 312 and the joining member 314. A compressive coil spring 328 is inserted into the accommodating space 318 in order that the valve plug 316 is constantly urged in the direction toward the closing plate 324 to close the slit 322 with a flange 326 of the valve plug 316.
The sleeve 304 is installed so that its end surface 304a can be flushed with an end surface 312a of the cylindrical member 312 of the first tube joint member 300. The sleeve 304 is always resiliently urged by the compressive coil spring 306 in the direction to make separation from the first tube joint member 300 toward the second tube joint member 302. However, the sleeve 304 is prevented from disengaging from the first tube joint member 300 by a ring-shaped stopper member 330 installed near the end surface 312a of the cylindrical member 312.
The cylindrical member 312 of the first tube joint member 300 has a plurality of holes 332 which are formed at positions of equal intervals in the circumferential direction of the cylindrical member 312 at a front end of the cylindrical member 312 (portion to overlap the second tube joint member 302). Each of the holes 332 has a diameter which is gradually reduced in the direction toward the central axis of the cylindrical member 312, and each of the ball members 308 is inserted into each of the holes 332. A part of the ball member 308 is inserted into and engaged with an annular groove 334 formed on the surface of the second tube joint member 302 when the second tube joint member 302 is inserted into the hollow of the cylindrical member 312. FIG. 6 shows only two of the holes 332 and the ball members 308 respectively.
Usually, the ball members 308 are pressed by the sleeve 304 in the direction toward the central axis of the cylindrical member 312. However, the ball members 308 are released from the pressing action of the sleeve 304 when an external force is applied to the sleeve 304 to move the sleeve 304 toward the joining member 314 in the axial direction of the tube joint member 300. At this time, the flange 326 of the valve plug 316 abuts against the closing plate 324 by being urged by the compressive coil spring 328 to close the slit 322. The valve plug 316 is thus closed.
Thereafter, when the second tube joint member 302 is inserted into the hollow of the cylindrical member 312 of the first tube joint member 300, the valve plug 316 is moved rearwardly against the urging action of the compressive coil spring 328 by the end surface of the second tube joint member 302. The valve plug 316 is thus opened.
When the external force having been applied to the sleeve 304 is eliminated, the sleeve 304 is resiliently urged by the resilient restoration of the compressive coil spring 306, and the sleeve 304 is restored to the position where the end surface 304a of the sleeve 304 is flushed with the end surface 312a of the cylindrical member 312.
Then, the ball members 308 are pressed again by the sleeve 304 in the direction toward the central axis of the cylindrical member 312. As a result, the ball members 308 are engaged with the annular groove 334 provided on the second tube joint member 302.
As a result of the engagement of the ball members 308, it is impossible for the second tube joint member 302 to disengage from the first tube joint member 300. The first and second tube joint members 300, 302 are firmly joined to one another.
The sleeve 304 may be deformed if an impact force is applied to the sleeve 304 of the above tube joint. Specifically, the sleeve 304 tends to be deformed if it has a thin-walled structure.
If the sleeve 304 is thus deformed, it is impossible for the sleeve 304 to move in the axial direction of the first tube joint member 300. It is consequently impossible to join or disengage from the second tube joint member 302.
Specifically, the sleeve 304 has a thin-walled structure to reduce the weight of the conventional tube joint in some cases. The thin-walled sleeve 304 may be deformed if it receives the external impact force. For example, the portion near the end surface 304a of the sleeve 304 and the other end section 304b thereof may highly possibly receive the impact force.
The impact force referred to herein is an excessive force which is not caused insofar as the sleeve 304 is usually handled. The impact force is different from the external force to move the sleeve 304 as described above. Specifically, it is possible to assume the impact force caused if the sleeve 304 is struck by a tool or the like or caused if the sleeve 304 falls to the ground or the floor.
If the sleeve 304 is deformed by the impact force, it is impossible for the sleeve 304 to move in the axial direction of the first tube joint member 300. It is further impossible for the ball members 308 to engage with or to be inserted into the groove 334. Not only the sleeve 304 but also the ball members 308 and the compressive coil spring 306 may be deformed.
Accordingly, the first tube joint member 300 and the second tube joint member 302 cannot be correctly joined to or disengaged from each other.
The sleeve 304 may have a thick-walled structure to prevent the above problem from occurring. However, in this case, it is not preferable that the weight of the entire tube joint may increase.
It is an object of the present invention to provide a tube joint which has a light weight and which is not broken and deformed even by an impact force caused if the tube joint falls to the ground or the floor.
The present invention provides a tube joint comprising a first tube joint member; a second tube joint member joined to the first tube joint member; a sleeve member attached to a joining portion of the first and second tube joint members, for joining and releasing the first and second tube joint members; a resilient member for urging the sleeve member in the direction to join the first and second tube joint members to one another; and a protecting member for protecting at least the sleeve member.
According to the present invention, it is possible to protect the sleeve member from the impact force caused if the tube joint member falls to the ground or the floor.
Stated otherwise, according to the tube joint of the present invention, it is possible to protect the joining portion of the tube joint from the impact force by the first and second protecting members and a holder. Components of the tube joint such as the sleeve member and a coil spring are not broken and deformed.
The sleeve member can be thin-walled by adopting the protecting member. Then, the size of the tube joint can be minimized and the weight thereof can be light.
Preferably, the protecting member is provided at least at a portion where the sleeve member can axially move at a forward end thereof. The forward end of the sleeve member is in the direction of the joining portion of the first and second tube joint members.
Preferably, the protecting member is provided at least at a portion where the sleeve member can axially move at a rear end thereof. The rear end of the sleeve member is opposite to the direction of the joining portion of the first and second tube joint members.
Preferably, the protecting members are provided at least at portions where the sleeve member can axially move at both of a forward end and a rear end thereof respectively. The forward end of the sleeve member is in the direction of the joining portion of the first and second tube joint members and the rear end of the sleeve member is opposite to the forward end thereof.
Preferably, the tube joint further comprises an engagement section for engaging with the protecting member, the engagement section being disposed at the forward end of the sleeve member. It is easy to engage with the protecting member if the engagement section is a recess.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.